Metabolic pathways for synthesis and interconversion of phospholipids will be assayed for in particulate cellular fractions of embryos, placentas, and yolk-sacs obtained from control and teratogen-treated pregnant rats. Also, the distribution of appropriate radiolabelled precursors into membrane-bound proteins or phospholipids will be determined by extraction of particulate fractions of control and treated rat embryos and their placentas. The fatty acid composition of the phospholipids extracted will be determined. BIBLIOGRAPHIC REFERENCES: East, J.M., K.P. Chepenik and B.M. Waite, 1975. Phospholipase A activities in rat placentas of 14 days gestation. Biochem. Biophys. Acta, 388: 106-112; East, J.M., K.P. Chepenik and B.M. Waite, 1975. Acyl-Co A: Lysophosphatidyl-choline acyl transferase activity in rat placentas of 14 days gestational age. Teratology, 11, No. 2: 16A (Abst.)